Rotary abrasive machine



April 14, 1931.

J. D. DAVIES ROTARY ABRASIVE MACHINE Filed Oct. 19, 1928 4 Sheets-Sheet l Ap 1931- J. D. DAVIES 1,800,341

I ROTARY ABRASIVE MACHINE Filed Oct. 19. 1928 4 Sh'ets-Sheet 2 April 14, 1931- .1. D. DAVIES 1,800,341

ROTARY ABRAS IVE MACHINE Filed Oct. 19, 1928 4 Sheets-Sheet 5 April 1931- 4 J. D. DAVIES 1,800,341

4 ROTARY ABRASIVE MACHINE I Filed Oct. 19, 1928 4 Sheets-Sheet 4 Jaiz'nflmama Patented Apr. 14, 1931 PATENT OFFICE JOHN D. DA VIES, OF SCRANTUN, PMSYLVANIA ROTARY AIBRASIVE MACHINE Application filed October 19,1928. Serial 1%. 313,505.

This invention relates to new and useful improvements in rotating abrasive machlnes used for the finishing or re-finishing of slate,

marble, wood, brass, copper and other metals 5 and materials for which it is adapted, and

more particularly for re-finishing marble and slate.

It is a well known fact that marble becomes stained, tarnished and scratched and that '10 slate black-boards, due to improper washing and removal of crayon, become coated and crystallized. Heretofore, this work has been done by hand and at great expense, because it was necessary to remove the slate or marble from the walls or place installed to a rubbing bench and hand rub it by various abrasives and then re-install it.

Recently certain portable motor driven machines have been in use attempting to eliminate the slow and expensive hand methods, but these machines have proven unsatisfactory and objectionable for various reasons. In at least one type of these machines, a vacuum system for the removal of the dust has been attempted, but has not been successful due to the fact that the power for driving the abrasive unit and vacuum producing unit is supplied by one and the same motor. In order to obtain the required finish, it is neces sary for the abrasive unit to be driven at a high and constant speed, and in order to remove 100 per centof the'dust, it is necessary for the vacuum unit also to be driven at a very high and constant speed and this can only be accomplished by the use of two separate and independant sources of power. This is due to the following facts: When a greater pressure is exerted against the surface to be refinished or a coarser carborundum disc is used, 40 a greater load is imposed on the driving unit with a consequent reduction in speed, and this results in a corresponding reduction in vacuum at the very time when a greater vacuum is required because of the greater amount of dust or cuttings being produced. With the use of the type of machine referred to above, as much as per cent of the dust has been lost and scattered throughout the air in the room. My machine will overcome all of the above objectionable features and will remove 100 per cent of the dust or cuttings by the use of two separate and independent systems operating at the cutting or grinding point. Further, my machine is so constructed that the cutting bit will re-finish marble, slate or other materials to the extreme edge of the exposed material without injury to or interference with trims, mouldings, or other surrounding materials used in connection with the finish 0f the same.

In the type of machine above referred to now in use, the method employed for holding or securing the carborundum disc to the rotating member is by means of a metal flange covering the outer surface of the disc for approximately three-quarters of an inch entirely around its periphery. This reduces the actual efi'ective working area of the disc by covering the very part which would be the most effective cutting area due to its higher speed and prevents it from cutting to the edges or extreme exposed surface of the work, necessitating that the rest of the work be finished by hand. Second, the housing for collecting the dust surrounds the rotating flanged disc with an annular space between, and this combined with the flange mentioned, leaves an unfinished edge around the work of approximately one and one-half inches. Moreover, the dust is thrown into the open air from the point of cutting over the flange to the annular space where it is supposed to be absorbed by the vacuum, but actually about forty or fifty per cent of the dust is thrown beyond this space and into the room.

In my machine, the cutting bit and disc are perforated for admission of the vacuum within their cutting area. In other words, my system of dust collection is an inner one by reason of the fact that the vacuum is applied at the point where the dust is produced within the cutting area instead of first throwing it into the open air and then trying to reclaim it by the vacuum.

\Vith the foregoing and other objects in view that will appear as the nature of my invention is better understood, the same consists in the novel features of construction,

combination and arrangement of parts illus ciated parts, with the parts shown on an enlarged scale.

Figure 3 is a vertical transverse section, taken on line 33 of Figure 2.

Figure 4 is a similar view, taken on line 4-4 of Figure 2.

Figure 5 is a detail perspective view of the bushing for clamping the center of the.

cutting disc in place.

Figure 6 is a face view of the cutting disc before bending.

Figure 7 is a view similar to Figure 1, showing the abrasive bit mounted directly on a small electric drill.

Figure 8 is a side elevation of the electric drill and theabrasive bit, the latter shown in section and the parts represented on an enlarged scale.

Figure 9 is a side elevation of a special tool used in tightening the bushingscrew in one form of thedevice and Figure 10 is a similar view of a special tool used in tightening the bushing screw in the other form of the invention.

Referring to the drawings for a more particular description of my invention and in which drawings like parts are designated by like reference characters throughout the several views, the numeral 1 represents the rotating member which carries the cutting disc and associated parts and will be hereinafter referred to as the bit. In the form of my invention shown in Figure 1, the bit 1 is driven through the flexible shaft 2 and in the form of my device shown in Figure 8, the bit is carried by the driving spindle 3 of an electric hand drill 4. In both forms of my invention, the bit is provided with an annular fiange'5 which carries the felt or rubber'pad 6, which acts as a cushion for the carborundum cutting disc 7 The cutting disc 7 is provided with a central open- -by an electric hand drill.

ter-sunk head 14 which fits against the inner wall or surface of the bushing and holds the latter firmly in place. The body portion or hub of the bit is also formed at the inner end of the bore 13 with a plurality of radial ports or openings 15, which communicate with the annular suction chamber 16 formed by the hollow semi-spherical housing 17. In the form of my device illustrated in Figure 1 of the drawings, the housing is secured to the bushing of the flexible shaft 2 by the tap 18 and in the form of my device illustrated in Figure 7, the air tube 19 of the housing is provided with a lug 20 to facilitate attachment to the electric hand drill 4 by the set screws 21.

The cutting disc 7 is provided adjacent its outer edge or perimiter with a circular series of spaced apertures 22 and the pad and annular flange of the bit 1 with corresponding registering apertures or orifices 23 and 24, re spectively. These apertures may "vary in size shape and number to meetdifferent requirements and said apertures provide for the ingress of the dust and dirt .laden air into the suction chamber 16 of the housing 17 The housing 17 is provided at its front edge with a felt packing ring 25 to prevent leakage of the air and the inner end of the" bit lis provided with a similar packing ring 26 to exclude dust and dirt from the bearings. The air tube 19 of the housing is connected with a standard flexible hose 27 which in turn is connected with a vacuum cleaner of any ordinary or approved type, in the usual way.

In the form of my device illustrated in Figure 1, the motor 29 is mounted on the standard portable pedestal 30 and the bit 1 is driven through. a flexible shaft as heretofore stated, whereas in the form of my invention shown in Figure 7 the bit is driven The machine is operated electricallyfrom the usual house current, either 110 or 220 volts, and cuts as required and where applied. In both forms of the device, the vacuum and grinding means are operated by independent motors and switches on both motors allow for the independent starting of the vacuum and grinding motors.

A special tool 31 is used for' tightening the hollow'bushing screw 12 in the form of the device shown in Figure 1, and a special tool 34 is used for tightening the hollow bushing screw 12, in the form of the device illustrated in Figure 7. The tool 31 is provided at its inner end with a square portion 32 adapted to engage a corresponding socket 33 in the bushing screw and the tool 34 is provided at its inner end with a chisel like portion 35 adapted to engage a corresponding slot or recess 36 in said screw. Both tools are provided at their extreme inner ends with pilots 37 to facilitate insertion.

My principle is applicable to stationary spindles in marble and slate plants using solid carborundum stones instead of discs and rubber or felt pads for the finishing and polishing of marble, slate and other raw materials prior to installations. From the foregoing description taken in connection with the drawings, it is thought that the construction, operation and advantages of my invention will be readily understood without requiring a more extended explanation.

Various changes in the form, proportions and minor details of construction may be re-. sorted to Without departing from the principles or sacrificing any of the advantages of my invention as defined in the appended claims.

Having described my invention, what I claim as new and desire to secure by Letters Patent, is

1. In a device of the character specified, a rotary bit provided with an annular flange having transverse passages and formed in its body portion with radial air openings, a cushioning member carried 'by the flange of the rotary bit and having transverse passages registering with those in said flange, an abrasive unit comprising a rotary cutting disc, positioned over the cushioning member and having transverse passages registering with those of the latter, a vacuum device, means associated with the vacuum device for creating a suctionthrough the transverse passages of the abrasive unit, cushioning member and flange of the rotary bit and the radial openings in the body portion of the latter, means for actuating the rotary bit and means comprising a tapering bushing and screw for removably securing the abrasive unit to the rotary bit.

2. In a device of the character specified, a rotary bit comprising a body portion formed in its outer end with a ta ering recess and with radial air openings be ind said recess and an annular flange provided with transverse passages, a cushioning member carried by the flange of the rotary bit and having transverse passages registering with those of the latter, an abrasive unit comprising a rotary cutting disc, positioned over the cushioning member and having transverse passages registering with those of the latter, said cutting disc having a central perforated portion bent inwardly against the wall of the tapering recess of the rotary bit, a knurled tapering bushing for clamping the central perforated portion of the cutting disc in place, a screw with a tapering head for securing the bushing in position, a vacuum device,

means associated with the vacuum device for nature.

JOHN D. DAVIES. 

